Hobbes's witty definition of the papacy as the ghost of the old Roman Empire sitting enthroned on the grave thereof, may tempt us to forget the all-important truth that the basis of the power of the ghost was essentially different from that of the dissolved body. The Empire was a political organisation, resting on military force. The Church was a social organisation, made vital by a conviction. The greatest fact in the intellectual history of the eighteenth century is the decisive revolution that overtook that sustaining conviction. The movement and the men whom we are studying owe all their interest to the share that they had in this immense task. The central conception, that the universe was called into existence only to further its Creator's purpose towards man, became incredible. This absolute proposition was slowly displaced by notions of the limitation of human faculties, and of the comparatively small portion of the whole cosmos or chaos to which we have reason to believe that these faculties give us access. To substitute this relative point of view for the absolute, was the all-important preliminary to the effectual breaking up of the great Catholic construction. What seems to careless observers a mere metaphysical dispute was in truth, and still is, the decisive quarter of the great battle between theology and a philosophy reconcilable with science. When the Catholic reaction set in, Joseph de Maistre, by far its acutest champion in the region of philosophy, at once made it his first business to attack the principle of relativity with all his force of dialectic, and to reinstate absolute modes of thinking, and the absolute quality of Catholic propositions about religion, knowledge, and government.[73] Yet neither he nor any one else on his side has ever effectively shaken the solid argument which Diderot fancifully illustrated in the following passage from his reply to Voltaire's letter of thanks for the opuscule: "This marvellous order and these wondrous adaptations, what am I to think of them? That they are metaphysical entities only existing in your own mind. You cover a vast piece of ground with a mass of ruins falling hither or thither at hazard; amid these the worm and the ant find commodious shelter enough. What would you say of these insects, if they were to take for real and final entities the relations of the places which they inhabit to their organisation, and then fall into ecstasies over the beauty of their subterranean architecture, and the wonderfully superior intelligence of the gardener who arranges things so conveniently for them?"[74] This is the notion which Voltaire himself three years afterwards illustrated in the witty fancies of _Micromegas_. The little animalcule in the square cap, who makes the giant laugh in a Homeric manner by its inflated account of itself as the final cause of the universe, is the type of the philosophy on which Catholicism is based.